Processes of continuous chemical nickel plating



D. E. METHENY Feb. 3, 1959 PROCESSES OF CONTINUOUS CHEMICAL NICKEL PLATING Filed Jan. l2, 1954 EL s IN V EN TOR.

PROCESSES F lCNTNUOUS CHEMICAL NICKEL PLATNG Donald E. Metheny, Hammond, Ind., assigner to General American Transportation Corporation, Chicago, Ill., `a corporation of New York Appiication January 12, 1954, Serial No. 403,596

17 Claims. (Cl. 117-130) The present invention relates to processes of continuous chemical nickel plating of catalytic materials; and it is the general object of the present invention to provide an improved process of the general character of that disclosed in the copending application of Paul Talmey and William I. Crehan, Serial No. 299,784, filed July 19, 1952, now Patent No. 2,717,218. v

The chemical nickel plating of a catalytic material employing an aqueous bath of the nickel cation-hypophosphite anion type is based upon the catalytic reduction of nickel cations to metallic nickel and the corresponding oxidation of hypophosphite anions to phosphite anions with the evolution of hydrogen gas at the catalytic surface. The reactions take place when the body of catalytic material is immersed in the plating bath, and the exterior surface of the body of catalytic material is coated with nickel.

The following elements are catalytic for the oxidation of hypophosphite anions and thus may be directly nickel plated: iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. The following elements are examples of materials which may be nickel nickel thereon either directly or through a galvanic eifect:

vcopper, silver, gold, beryllium, germanium, aluminum,

carbon, vanadium, molybdenum, tungsten, chromium, se- `lenium, titanium and uranium. The following elements are examples of non-catalytic materials which ordinarily may not be nickel plated: bismuth, cadmium, tin, lead and Zinc. The activity of the catalytic materials varies considera-bly and the following elements are particularly good catalysts in the chemical nickel plating bath: iron, cobalt, nickel and palladium. The chemical nickel plating process is autocatalytic since both the' original surface of the body being plated and the nickel metal that is deposited on the surface thereof are catalytic; and the reduction of the nickel cations to metallic nickel in the plating bath proceeds until all of the nickel cations have been reduced to metallic nickel, in the presence of an excess of hypophosphite anions, or until all of the hypophosphite anions have been oxidized to phosphite anions, in the presence of an excess of nickel cations.

ln a batch plating process, the reactions are sloweddown rather rapidly as time proceeds because the anions, as contrasted with the cations, of the nickel salt that is dissolved in the plating bath combine with the hydrogen cations to form an acid, which, in turn, lowers the pH of the bath; and the .reducing power of the hypophosphite anions is decreased as the pH value of the bath decreases'. g

On the other hand, in a continuous plating process, the reactions are. maintained substantially at their initial rates by the regeneration of the plating bath; i. e., by the adding thereto of soluble nickel-containing and liypophosphitecontaining reagents, as well as an alkalizing reagent for pH control. Thus the regeneration of the bath during 2 tageous pH of the plating bath to assure'a high plating rate.

In the previously-mentioned Talmey and Crehan application, there is disclosed a continuous nickel plating process and system that is particularly well-suited to commercial production; which system involves periodic or continuous regeneration of the plating bath by the addition thereto of appropriate ingredients for the purpose of maintaining substantially constant both the fundamental composition and the pH thereof. More specifically, in this system, there vare provided a reservoir, a condenser, a plating chamber, primary and secondary vacuum dash tanks and primary and secondary steam jetpumps. In the system, a first portion of the plating solution is stored at a relatively low temperature well below the boiling point thereof and at a relatively high concentration in the reservoir; and a second portion of the plating solution is held .as a bath at a relatively high temperature slightly below the boiling point thereof and at a relatively low concentration in the plating cham-ber. In the system, the plating solution is pumped from the reservoir into the condenser and therein it is subjected to the discharge of the primary steam jet pump, the primary steam jet pump also communicating both with a source of high pressure steam and with the primary vacuum flash tank; whereby water vapor is withdrawn from the plating solution in the primary vacuum flash tank and is combined with the steam and projected into the condenser; whereby the plating solution in the condenser is both heated substantially to the desired temperature and diluted substantially to the desired concentration. From the condenser, the plating solution is conducted into the plating chamber and thence into the primary vacuum flash tank. In the primary vacuum Hash tank, the plating solution is subjected to an initial concentration by the withdrawal of water vapor therefrom; which water vapor is supplied to the primary steam jet pump, as noted above. From the primary vacuum flash tank, the plating solution is conducted into the secondary vacuum flash tank; whereby further water vapor is withdrawn therefrom by the secondary steam jet pump and discharged to the atmosphere so that the plating solution thus conthe plating of the catalytic material maintains not only the desirable nickel cation concentration and hypophosphite anion Concentration, but also preserves the most4 advany centrated is returned to the reservoir and recirculated. In the primary and secondary vacuum liash tanks, the plating solution is concentrated, as noted above, and is also cooled to the desired temperature before the return thereof to the reservoir. In the system, the removal of the water vapor from the plating solution in the secondary vacuum flash tank, and the discharge of this water vapor to the exterior, compensates for the water that is added to the plating solution in the condenser as a result of the operation of the primary steam jet pump; whereby there is no continuous and undesirable build-up of water in the circulated plating solution. Y Further, the reservoir is arranged to provide a storage compartment and a communieating regeneration compartment, the plating solution being returned from the secondary vacuum flash tank into the regeneration compartment and being supplied to the condenser from the storage compartment. Further in the system, the previously-mentioned ingredients that are employed for the purpose of regenerating the plating solution are `added thereto in the regeneration compartment of the reservoir in order to insure proper and thorough dissolving and mixing thereof prior to transfer into the storage compartment and subsequent circulation of the plating solution in the system. Finally, in the system, the body of catalytic material that is to be nickel plated, or a series of such bodies, are immersed in the plating chamber and subsequently withdrawn therefrom after a time interval corresponding to the thickness of the nickel plating thereon that is desired.

A number of suitable aqueous chemical nickel plating aeraaas baths of the nickel cation-hypophosphite anion type that may be employed in the continuous nickel plating system of the Talrney and Crehanapplication are disclosed in U, S.. Patent No. 2, 658,841, granted on November l0, 1953, to Gregoire Gutzeit andAbraham Krieg, and U. S. Patent No. 2,658,842, granted on November 10, 1953, to Gregoire Gutzeit and Ernest I. Ramirez, and in the copending application of Gregoire Gutzeit, Paul Talmey and Warren G. Lee, Serial No. 376,968, filed August 27, 1953, now abandoned. In the continuous plating system, the

application are preferred -both from the standpoint of economy and of performance; and three examples of such aqueous plating baths may be designated: The malic acidlactic acid-succinate bath, the malic acid-glycine bath and the malic acid-succinate bath.

A typical malic acid-lactic acid-succinate plating bath comprises: an absolute concentration of hypophosphite 'anions in the range0.l5 to 1.20 moles/liter; a ratio between nickel cations and hypophosphite anions in the range 0.25 to 1.60; an absolute concentration of malic 'acid anions in the range 0.04 to 0.20 mole/ liter; an absolute concentration of lactic acid anions in the range 0.04

to 1.00 mole/liter; the total quantity of the rnalic acid anions and the lactic acid anions are sufficient to complex at least 100% of the nickel cations; an absolute concentration of succinateV acid anions of at least 0.04 mole/ liter; and a pH within the range 4.5 to 7.0.

A vtypical malic acid-glycine plating bath comprises: an

absolute concentration of hypophosphite anions in the i.

range 0.15 to 1.20 moles/ liter; a ratio between nickel cations and hypophosphite anions in the range 0.25 to 1.60; an absolute concentration of malic acid anions suicient to complex at least 100% of the nickel cations; and an absolute concentration of glycine anions of at least 0.04 mole/liter; and a pH within the range 4.5 to 9.5.

A typical malic acid-succinate plating bath comprises: an absolute concentration of hypophosphite anions in the lrange 0.15 to 1.20 moles/liter; a ratio betweennickel cations and hypophosphite anions in the range 0.25 to 1.60; an absolute concentration of malic acid anions sufcient to complex at least 100% of the nickel cations; an absolute concentration of succinate'anions of at least 0.04 mole/liter; and a pH'within the range 4.5 to 6.0.

In the formulation of any one of these plating baths,

'an aqueous solution is prepared of the ingredients named;

the nickel cations may be derived from nickel chloride, nickel sulfate, etc., or various combinations thereof; the

hypophosphite anions may be derived from sodium, potassium, etc., hypophosphites, or various combinations there- Gof;A the other additives are introduced into the bath normally as `the acids, or as the Vsoluble salts thereof, etc.; arid the desired pH of the bath is established by the eventual introduction thereinto of an acid or a base, as required; hydrochloric acid and Vsodium hydroxide being recommended, as a matter of economy and simplicity.

inv the compositions of the various plating baths, the

terms cation, anion and ion, as employed, include Vthe total quantity of the corresponding elements that are present in the plating bath; i. e., both undissociated and dissociated material. in other words, 100% dissociation is assumed when the terms noted are used in connection with molar ratios and concentrations in the plating bath.

ln carrying out the continuous process of the Talmey and Crehan application, the matter ofthe regeneration of the aqueous plating solution in the regeneration compartment of the reservoir is simple in principle, but exceedingly tedious in practice, as thequantities of ingredients -that'must be supplied thereto haveto be determined either largely from experience or from elaborate calculations involving the pH deviation thereof and the weight of the nickel plating that hasV been laid down or deposited therefrom upon the 'catalytic body or bodies. 'Moreoven in this regeneration of the plating solution, the utilization of experience' as a guide is subject to considerable human er- Talrney and Crehan application, there is a great need for 15 a simple highly accurate scheme for determining the plating baths disclosed in the Gutzeit, Talmey and Lee quantities of the required ingredients that must be employed in the regeneration compartment of the reservoir for the purpose of maintaining the initial composition of the plating solution so as to obtain the optimum advantages of a fast plating rate, a greatstability, etc.

Accordingly, it is 'another object of the invention to provide a continuous chemical nickel plating process of the character described that involves improved, simple and fast manipulative steps rendering highly accurate proper regeneration of the aqueous chemical plating solution.

The present invention is predicated upon the discovery that as the continuous chemical nickel plating process is carried out, the decrease in the pH of the aqueous plating solution from its initial Value is directly related, not only to the amount of alkalizing reagent that must be supplied thereto to restore the initial pH thereof, but to the amount of both the nickel salt and the hypophosphite that must be added thereto for the purpose of restoring the fundamental initial composition thereof. Now the matter of measuring, either continuously or periodically, the pH of the aqueous plating solution is a simple operation involving the utilization of a pH meter or controller; whereby the necessary total amount of alkalizing reagent to be supplied to the plating solution for regeneration purposes may be determined either by calculation in view of the known volume of the plating solution or empirically by simply adding enough alkalizing reagent to restore the initial pH of the plating solution. Having thus established the total amount of alkalizing reagent that is required for purpose of regeneration of the plating solution, the total amounts of nickel salt and hypophosphite that are also required for the purpose of regeneration are automatically established, since the required total amount of nickel salt and the required total amount of hypophosphite are directly related to and proportional to the required total amount -of alkalizing reagent.

Thus, in accordance with the present invention, in the continuous chemical nickel plating operation, the regeneration of the plating solution'rnay be carried out either continuously or periodically, as is convenient, merely by following the pH meter or controller and utilizing the addition of alkalizing reagent as a reference for establishing the additions of nickel salt and hypophosphite.

Further features of the invention pertain to the particular arrangement of the steps of the method, whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawing, in which the single ligure is a diagrammatic illustration of a continuous nickel plating system in which the process of the present invention may be carried out.

Referring now to the drawing, the continuous chemical nickel plating system there illustrated, and suitable for the carrying out of the present process, is essentially of the arrangement disclosed in the previously-mentioned '.Talmey and Crehan application. More particularly, the

system fundamentally comprises a reservoir 11, a plating tank or chamber 12, a condenser 13, a primary vacuum flash tank'14, a secondary vacuum flash tank 115,4 a primary steam jet pump 16, a secondary steam jet pump 17, and a mechanical pump 18. The reservoir 11 includes a ballled storage compartment 19 and a communicating regeneration compartment 20, the regeneration compartment 20 being provided with agitator mechanism 21 driven by an associated electric motor 22. In the arrangement, the inlet ofthe pump 18 communicates with the upper portion of the storage compartment 19; and the outlet of the pump 18 communicates with the upper portion of the condenser 13. The lower portion of the condenser 13 communicates with the upper portion of the plating tank 12; and the lower portion of the plating tank 12 communicates with the upper portion of the primary vacuum Hash tankA 14. The lower portion of the primary vacuum ash tank 14 communicates with the upper portion of the secondary vacuum flash tank 15; and the lower portion ofthe secondary vacuum flask tank 15 communicates with the upper portion of the regeneration compartment 20. Also, the upper portion of the primary vacuum flask tank 14 communicates with the primary steam jet pump 16, that is also connected to an associated source of high pressure steam, not shown; and the discharge of the primary steam jet pump 16 communicates with the upper portion of the condenser 13. Also, the upper portion of the secondary vacuum ash tank 15 communicates with the secondary steam jet pump 17, that is also connected to the associated source of high pressure steam, not shown; and the discharge of the secondary steam jet pump 17 communicates with the atmosphere. The system contains an aqueous plating solution of 'the character previously described; whereby a first portion of the plating solution is stored in the reservoir 11 at a relatively low temperature well below the boiling point thereof and in a relatively concentrated form; while a second portion of the plating solution is held as a bath in the plating tank or chamber 12 at arelatively high temperature slightly below the boiling point thereofand in a relatively dilute form. Of course, the composition of the plating solution in the plating tank 12 is that previously set forth and disclosed in the previouslymentioned Gutzeit, Talmey and Lee application.

In the operation of the system, the plating solution in the storage compartment 19 may havea temperatureof about 150 F.; while the plating solution in the plating tank 12 may have a temperature of about 210 F.' The plating solution is circulated from tlie upper portion of the storage compartment 19 by the pump- 151 into the upper portion of the condenser 13, wherein it is both heated to the required temperature of about 210 F., and

diluted to the required concentration by the discharge from the primary steam jet pump 1,6. 'The dilution of the plating solution in the condenser 13 is achieved not only by the introduction of the steam thereinto, but also by the introduction of the water vapor thereinto that 1S withdrawn from the upper portion of the primary Vacuum ash tank 14. The plating Solution from the condenser 13 is circulated into the plating tank 12. and thence into the upper portion of the primary vacuum ash tank 14, and therefrom into the upper portion of the secondary vacuum flash tank 15, and ultimately back into the upper portion of the regeneration compartment 2G. In the primary vacuum flash tank 14, a vacuum of about 12 Y Hg is drawn by the primary steam jet pump .16; whereby water vapor is withdrawn from the contained plating solution, as previously noted, so that the plating solution in the primary vacuum ash tank 14 is both concentrated and cooled. In the secondary vacuum flash tank 15, a vacuum of about 22 Hg is drawn by the secondary steam jet pump 17; whereby water vapor is withdrawn therefrom, so that the plating solution in the secondary flash tank 15 is both concentrated and cooled prior to the return thereof to the regeneration compartment 20. The plating solution returned into the regeneration compartment may have a temperature of about 150 F.,

,as previously noted, as a consequence of the tandem cool- 6 ing effects produced in the primary and secondary vacuum flash tanks 14 and 15. Also, the plating solution thus returned to the regeneration compartment 20 is in the relatively concentrated form as a consequence of the tandem concentrating effects produced in the primary 'and secondary vacuum flash tanks 14 and 15. Since the discharge of the secondary steam jet pump 17 is to the atmosphere, the water Vapor withdrawn from the plating solution in the upper portion of the secondary vacuum flash tank 15 prevents the build-up of water in the circulated plating solution; and preferably the weight of steam introduced into the plating solution in the condenser 13 by the primary steam jet pump 16 substantially equals the weight of the water v apor withdrawn therefrom in the secondary vacuum flash tank 15 and discharged to the atmosphere by the secondary steam jet pump 17; thereby maintaining the desired balance of the water supplied to and extracted from the circulated plating solution. Y

The catalytic bodies are immersed in the plating bath in the plating chamber 12; whereby the metallic nickel (actually an alloy of nickel and phosphorus having a composition of about 89% to 97% nickel `and 11% to 3% phosphorus by weight) is deposited upon the surfaces thereof; the bodies being withdrawn from the plating bath when the coatings thereon are of the desired thickness. Incident to the plating of the nickel upon the catalytic bodies the initial composition of the plating bath is altered by the reduction of the nickel cations and the oxidation of the hypophosphite anions, as previously noted; and the initial pH of the bath is reduced, as previously explained; whereby it is necessary to regenerate the plating:

solution in the regeneration compartment 2t) by the addi-- tion thereto of an alkalizing reagent to restore the initial pH thereof and of a nickel salt and a hypophosphite to restore the initial composition thereof; the ingredients thus supplied in the regeneration compartment 2t) being thoroughly dissolved therein by operation of the agitator mechanism 21 from the electric motor 22. As a matter of convenience, the added alkalizing reagent may be derived from an aqueous sodium hydroxide stock solution; and assuming that the initial bath was formulated utilizing nickel chloride and sodium hypophosphite, the added nickel salt may be derived from an aqueous nickel chloride stock solution and the added hypophosphite may be derived from an aqueous sodium hypophosphite stock solution. Of course, the exact initial composition of the plating solution is not restored as it is apparent there is a gradual build-up therein of sodium cations and chlorine anions, `as a result of the additions, as well as a gradual build-up of phosphite anions, as a result of the plating reactions. However, this build-up of the foreign cations and anions named is gradual and of small moment until the phosphite anion concentration builds up to about one mole per liter; whereby the aqueous plating solution may be employed continuously in the plating system throughout the corresponding time interval, provided it is appropriately regenerated, either continuously or periodically, as explained above.

Initial Ratio Ratio Ratio pH Ni++/OH Hypo-[NB+ Hypo/OH- 0. 500 3. O l. 500 0. 479 3. 0 l. 437 0. 458 3. 0 l. 374 0. 438 3. 0 l. 287 0. 417 3. 0 l. 251

From the foregoing table. it will be observed that the ratio between the nickel cations and the hydroxyl anions that must be added in the regeneration of the plating solution is dependent upon the initial pH thereof.y the ratio varying substantially linearly inversely with the initial pH of thev plating solution. whereas the rates of hypophosphite anion and nickel cation utilization bear a lixed ratio ot 3:1 independently of the initial pl-l of the plating solution. Thus, thek ratio of hynonhosphite anions and the hydroxyl anions that must be in the regeneration of the plating solution is also dependent upon the initial pH of the plating solution, the ratio varying substantially linearly inversely with the-initial pH of the plating solution. Of course` the total amountV of hydroxyl anions that must be added in the regeneration o? the plating solution fora given change in pH is dependent upon the volume of the plating solution, and is related to the total amount of nickel platingthat has been laid down in the plating chamber.

First, assuming that the regeneration ol'i thc plating solution is carriedv out periodically, it is recommended that the permitted departure from the initial pH thereof` is within the approximate range 3% to 4%. Thus, when the pH of the plating solution departs about 3% to 4% from the initial pH thereof, a controlled amount of hydroxyl anion stock solutionis added thereto in order to restore the initial pI-l thereof. ln view of this controlled addition of the hydroxyl anion stock solution to the Plats ing solution, the predetermined, required, related and controlled additions of the nickel cation stock solution and the hypophosphite anion stock solution are made; whereby the plating solution is restored to its initial pH and the initial composition thereof, with respect to nickel cations and hypophosphite anions, is restored. Thus, in the continuous operation of the system, neither the pH nor the composition of the plating solution varies substantially from the initial value thereof; whereby the nickel plating is carried out under optimum conditions with respect to rate, stability, etc.

On the other hand, the regeneration of the plating solution may be carried out continuously, instead of periodically, as described above, by setting the proper rate of addition of the hydroxyl anion stock solution to the plating solution so as to maintain substantially constant the initial pH of the plating solution, and by setting the predetermined, required,.related, and controlled rates of addition of the respectivek nickel cation stock solution and hypop'nosphite anion stock solution.

Again referring to the drawing, a-pH meter or conv troller 23 may be provided that includes aV pair of control electrodes 2id/and. 25 arranged in the upper portion of the storage compartment i9; whereby the pH con-- troller 2.3 is governed in accordance with the pH of the plating solution inV thel storage compartment E9. Moreover, the system comprises first, second and third. stock solution tanks 261, 27 and. 28 respectively containingI the aqueous hydroxyl anion stock. solution, the aqueous nickel cationv stock solution and the aqueous hypophosphite anion stock solution, as well as a water tanlt 29. The four tanks 26, 27, 2S andi 29 respectively cornrnuuicate with the upper portion of the regeneration cornpartment 2t? via four conduits Sil, 3l, 32. and 33, th respectively include four manual shut-oil valves 34', 36 and E57, four automatic solenoid. valves 38, 39, fit? and ill, and four ilow regulators 42, 43, 44 and 45. The automatic solenoid valves 38, 39 and ill maybe commonly controlled by the pH controller 23; while 'the automatic solenoid valve d?. is controlled by an associated manual controller 46. In the arrangement, the tlow regulators 42, etc., may be selectively set to govern the liquid e flow through the associated conduits 30, etc., into the upper portion of the regeneration compartment 20.

As a matter of manipulation, the three stock solutions respectively contained in the tanks. 26, 27 and 2S may be of the same and fixed molar concentrations; whereby the flow regulators 42, 43 and. 44 may be selectively ad ously explained; whereby the ow regulators 42, 43 and 44 may be adjusted to accommodate liquid flow through the respective conduits 30, 3l and $2 at the same, xed and uniform rate, when the automatic solenoid valves 3S, 39 and' di) are opened. In either case, the molarquantities of ions supplied via the conduits 30,. 3l. and 222 into the upper portion of the regeneration compartment 2li bear the previously-explained relationships with respect to each other. Moreover, it will be understood that the matter of the direct or indirect control by the pH troller 23` ofv the automatic solenoid valves 33,- 39 and d6 is a matter of choice; and likewise, the matter of whether this control by the pH controller 23 is exercised periodically or continuously is also one of choice. in the various plating tests appearing hereinafterweights of nickel plating deposited are reported in gms.; and plating rates are reported in gni./cm.2/min.

, Considering now a continuous plating test, an aqueous plating bath of they malic acid-lactic acid-succinate type was employed that had the particular composition:

M. p. l. Nickel chloride 0.0675 Sodium hypophosphite 0.225 Malic acid 0.06

Lactic acid 0.2025 Sodium succinate 0.12

Utilizing. this plating bath, properly cleaned steel samples of 80 cm? were plated. The bath was employed in a continuous plating system of the character described, having a plating chamber volume of 300 cc., the volume ci the oath being 9 liters, and the temperature thereof in the plating chamber being about 100 C. in this continuous plating test, the plating bath was regenerated after. each cycle by the addition of therequired proportions of the three stock solutions, as previously explained, and with the following results:

5g. Cycle No; 1 2 3 4 5 o 7 Initial pH 4.74 4. 75 4.72 4.75 4.75 4.73 4.77 Final pH 4. 4.59 4.62 4.61 4.60 4.66 4.68 Wt. gam, gms 4, 57 3. GS 4.00 3. 80 3. 75 Lt. 07 4.20 Time, min 123 101 95 8S 10:3 123 127 Soin. Flow rate, oc./rnin 47 5S 60 65 54 t6 45 il Plating rate, RXlOl 4.85 4.55 5.08 5. 4G 4.45 4.14 4.14

the particular composition:

Mp1. Nickel chloride 0.0675 Sodium hypophosphite 0.225 Malic acid 0.135 Aminoacetic acid 0.0675

Utilizing this plating bath, properly cleaned steel saml ples of Sil cm.2 area were plated. The plating bath was employed in a continuous plating system of the charac.` ter described, having a plating chamber volume of. 300

cc., the volume of the bath being one liter, and the temperature thereof in the plating chamber being about 100rl C. In this continuous plating test, the plating bath was regenerated after each cycle by the addition of the rewith reference to the high plating rate and the stability thereof. Moreover, since the composition of the bath and the plating rate are su "stantially uniform in the plating chamber the resulting coating on the steel object quired proportions of the three stock solutions, as previ- 5 is substantially uniform and homogeneous throughout. ously explained, and with the following results: In passing, it is noted that in the event of regeneration y of the plating bath after permitting wide variations of Cyde Nt, 1 2 3 4 5 6 7 either the initial pH or the initial composition thereof, the nickel coating that is applied to the steel object is 6.68 5 51 5,45 6 2; 5 98 10 stratified, thus lacking the desired uniformity and homot 5. 90 5.99 5.69 5.90 5. 82 geneity menti0ned 'siiinamm 'il 615g 7ig @iig 4'M528 In the continuous nickel plating process, the water 0 u; OW fate CC- min" 47 57 59 57 46 52 57 content of the plating solution is maintained substantially Platmg rateRXlO 497 6'70 7'02 7'84 7'75 6'96 5'63 balanced by the introduction of steam thereinto in the In the regeneration of this plating bath, since the initial gl jrpngylglal s; 111; gttligl 2 glaeter/n PH thereof las about 65 a rat1o-between me addltlons therefrom in the secondary vacuum ash tank 15 by of nckel canons and hydroxyl among of, 0'417 .was em virtue of the action of the secondary steam jet pump 17; ployed; and-the c onstant milo *be/[Wien me :additions of and any small additions of water that are required may hypophosphite anions and nickel cations of .2.0 was em' 20 be provided from the water tank 29 by selectively governployed I ing the manual controller 46. Moreover, the matter of In fulther conupuou? platlllg test an aqueous plat' regenerating the plating solution with respect to the mg balh of the @alle acld'suclilat type was employed other initial special ingredients thereof; i. e., malic acid, that had the Particular Composmon' M p l lactic acid and succinate, in a plating bath of the malic v 25 acid-lactic acid-succinate type, is not particularly critical, Nickel chlonde ""7 0'675 since these special ingredients are expended only very Sodlllm llypophosphlte 0'225 gradually over an exceedingly long time interval; whereby Mam: amd 0'135 addition of these special ingredients may be required Sodium succmate 006 only two or three times during the whole lifetime of a Utilizing this plating bath, properly cleaned steel samplating solution that has been regenerated a great many ples of 80 cm.2 area were plated. The plating bath Was times with respect to the hydroxyl anions, the nickel employed in a continuous plating system of the charcations and the hypophospliite anions, as described above. acter described, having a plating chamber volume of Furthermore, the matter of the replenishing of these 300 cc., the volume of the bath being one liter, and the special ingredients is exceedingly simple in View of the temperature thereof in the plating chamber being about lack of criticality of the content thereof for entirely satl00 C. In this continuous plating test, the plating bath isfactory plating results; whereby small amounts of these was regenerated after each cycle by the addition of the special ingredients are added to the plating solution from required proportions of the three stock solutions, as previtime to time during the whole lifetime thereof, as reously explained, and with the following results: quired.

Cycle No 1 2 3 4 5 6 7 8 Initiaipi 5.39 5. 37 5.33 5.37 5. 38 5.44 FinaipH; 4.91 5. 07 4.99 5.1i 5.07 5.28 Wt. gain (gms) 3. 62 4.82 3. 50 4.03 5.00 4. 96 Tmiamin 100 126 94 103 125 121 Soln. how rate, ce. 57 45 61 55 45 47 Plating rate, R 104 4. 53 4. 77 4.13 4.90 4. 96 5.13

In the regeneration of this plating bath, since the initial in the foregoing examples, the plating solutions were pH thereof was about 5.4, a ratio between the additions o regenerated employing the aqueous stock solutions conof nickel cations and hydroxyl anions of 0.463 was emtaining sodium hydroxide as the alkalizing reagent, but ployed; and the constant ratio between the additions of it will be understood that other water-soluble alkalizing hypophosphite anions and nickel cations of 3.0 was emreagents, such as other hydroxides, carbonates, bicarployed. bonates, etc., may be used. When any one of these al- In connection with the continuous nickel plating procteriiative alkalizing reagents is employed, the alkalizing ess, it is noted that the article to be nickel plated, and equivalen@ thereof With respect t0 Sodium hydroxide is normally having a catalytic surface, is first properly rSt established and emplOyed in making up the correprepared by mechanical Cleaning, degreasing and light sponding aqueous stock solution, before proceeding with pickling, substantially in accordance with standard prac- 60 the regeneration of a plating solution, utilizing the proper tices in electroplating processes, prior to the immersion PrOpOrtOnS Of the three stock solutions, in accordance thereof in the plating chamber. For example, in the 'With the present process. nickel plating of a steel object, it is customary to clean In View of the foregoing, it is apparent that there has the rust and mill scale from the object, to degrease the been provided a continuous chemical nickel plating procobject, and then lightly to pickle the object in a suitess highly suitable for use on a commercial scale that able acid, such as hydrochloric acid. Subsequently, the involves simple and highly accurate manipulations for steel object is removed from the bath after an appropridetermining the quantities of the required ingredients ate time interval corresponding to the required thickness that must be employed in the regeneration of the plating of the nickel coating deposited thereon that is desired; solution and for effecting the addition thereto of the reand ultimately the steel object is rinsed off with water quired amounts of theingredients to obtain proper regenand is then ready for use. Y eration of the plating solution.

During the plating of the steel object, the plating bath While there has been described what is at present conis regenerated, in the manner previously explained, so sidered to be the preferred embodiment of the invention, as to prevent any substantial departure of the plating bath it will be the preferred embodiment of the invention, it from either its initial pH or its initial composition; will be understod that various modifications may be made whereby the advantages previously explainedare obtained therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is: Y

l; The continuous process of chemically plating with nickel a solid body of catalytic material, which consists of providing an :aqueous chemical nickel plating of the nickel cation-hypophosphite anion type and 'nav' both a given initial composition and a given initial pir, contacting said body with saidbath during a ti-- e interval in order to effect the reduction of nickel ca i. to metallic` nickel and the deposition thereof upf` f surface of said `body along with the companion o of hypopnosphite `anions to phospliite anions and resulting in the depletion of both nickel cations and hypopho-sphite anions in said bath and in thecor decrease in the pH thereon, measuring the bath during said time interval adding to said atiA said time interval and as determined by said urement a measured amount of alkalizing reagent that is sufficient substantially to restore said given initial pH thereof, adding to said bath during said time interval a measured amount of nickel cations that is related substantially in a Vfirst `fixed proportion to the measu amount of alkalizing reagent added thereto, and ade' V. to said bath during said time interval a measured amount of hypophosphite anions that is related substantially in a second fixed proportion to the measured amount of nickel cations added thereto, said measured additions of nickel cations and of hypophosphite anions substantially restoring said given initial composition of said bath.

2. The continuous process of chemically plating with nickel a solid body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which consists of providing an aqueous chemical ickel plating bath of the nickel cation-hypophosphite anion type and having both a given initial composition and a given initial pH, contacting said body with said bath during a time interval in order to effect the reduction of nickel cations to metallic nickel and the deposition thereof upon the surface of said body along with the companion oxidation of hypophosphite anions to phosphite anions and resulting in the depletion of both nickel cations and hypophosphite anions in said bath and in thevcorresponding decrease in the pH thereof, measuring the pli of said bath during said time interval, adding to said bath during said time intervalvand as determined by said pH measurement a measured amount of alkalizing reagent that is sufficient substantially to restore said given initial pH thereof, adding to said bath during said time interval a measured amount of nickel cations that is related substantially in a first fixed proportion to 'the measured amount of alkalizing reagent added thereto, and adding to said bath during said time interval a measured amount of hypophosphite anions that is related sub-- stantially in a second iixed proportion to the measured amount of nickel cations added thereto, said measured additions of nickel cations and of hypophosphite anions substantially restoring said given initialk composition of said bath.

3. "Ehe continuous process of chemically plating with nickel a solid lbody essentially comprising an element selected from the group 'consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which consists of providing a bath of an aqueous solution of a nickel salt and a hypophosphite and having both a given initial composition and a given initial pl-l, con* tasting said body with said bath during a time interval in orde to edect the reduction of nickel cations to metallic nickel and the deposition thereof upon the surface of said body along'rwith the companion oxidation of 'hypophosphite anions to phosphite anions and resulting in the depletion of both nickel cations and hypophosphite anions insaidbatnand in the corresponding decrease inthe pH thereof, measuring the pH `of saidY bath during said time interval, adding to said bath during said time interval and as determined `by said pH measurement a measured amount of a hydroxide that is suicient substantially to restore said given initial pH thereof, adding to said bath during said time interval a measured amount of a nickel salt is related substantially in a first fixed proportion to the measured amount of hydroxide added thereto, and adding to said bath during said time interval a measured amount of a hypophosphite that is related substantially in a seco-nd lixed proportion to thev measured amount of nickel sait added thereto, said measured additions of nickel salt and of hypophosphite substantially restoring said given initial composition of said bath.

4. The continuous process of chemically plating with nickel a solid body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which consists of providing an aqueous chemical nickel plating bath of the nickel cation-hypophosphite anion type and having both a given initial composition and a given initial pH, contacting said body with said bath during a time interval in order to effect the reduc" n of nickel cations to metallic nickel and theV deposition thereof upon the surface of said body along with the coinpanion oxidation of hypophoshite anions to phosphite anions and resulting in the depletion of both nickel cations and hypophosphite anions in said bath and in the corresponding decrease in the pH thereof, measuring the pH of said oath during said time interval, adding to said bath during said time interval and as determined by said pil measurement a measured amount oydroxyl anions lthat is suiiicient substantially to resto-re said given initial ypli-l thereof, adding Vto said bath during said time iflerval a measured amount of nickel cations is related substantially in a first xcd proportion to the m isured amount of hydroxyl anions added thereto and adding to said bath during said time interval a amount of hypcphosphite anions that is related sm. tially in a second fixed proportion to the red amount of nickel cations added thereto, sa d measured additions of nickel cations and of hypophosplxite anions substantially restoring said given initial composition of said bath.

5. The continuous process set forth in claim 4, wherein said given initial pH is in the approximate range 4.5 to 6.5, said first fixed proportion expressed as a ratio between added nickel cations and added hydroxyl anions is in a corresponding approximate range 0.50 to 0.42, and said second fixed proportion express-cd as ratio between added hypophosphite anions and added nickel cations is approximately 3.

6. The continuous process set forth inclaim 5, wherein the variation of said irst fixed proportion in said range 0.50 to 0.42 is substantially inversely linear with theV variationof the pH of said bath in said range 4.5 to 6.5; whereby said rst fixed proportion has the approximate values of 0.500, 0.479, 0.458, 0.458 and 0.417 at the respectively corresponding pH values of 4.5, 5.0, 5.5, 6.0 and 6.5.

7. The continuous process set forth in claim 4, wherein said given initial pH is approximately 4.5, said first fixed proportion expressedV as a ratio vbetween added nickel cations and added Vhydroxyl anions is approximately 0.5, and said second fixed' proportion expressed as a ratio between added hypophosphite anions and added nickel cations is approximately 3.

8.7The continuous process r-sct forth in claim 4, wherein said additions of hydroxyl anions and of nickel cations and of hypophosphite anions to said bath are made substantially simultaneously.V

9. The continuous process set forth in claim 4, wherein said given initial composition of said bath is substantiallyas follows: the ratio between nickel cations and hypophosphite anions is in the approximate range 0.25

to 1.60, and the absolute concentration of hypophosphite anions is in the approximate range 0.15 to 1.20 moles/ liter; and wherein said given initial pH of said bath is in the approximate range 4.5 to 6.5.

l0. The continuous process of chemically plating with nickel a solid body essentially comprising an element selected from the group consisting of iron, cobalt, nickel,

aluminum, copper, silver, go-ld, palladium and platinum,

which consists of providing an aqueous chemical plating bath of the nickel cation-hypophosphite anion type and having both a given initial composition and a given initial pH, contacting said body With said bath during a time interval in order to effect the reduction of nickel cations to metallic nickel and the deposition thereof upon the surface of said body along with the companion oxidation of hypophosphite anions to phosphite anions and resulting in the depletion of bo-th nickel cations and hypophosphite anions in said bath and in the corresponding decrease in the pH. thereof, repeatedly measuring the pH of said `bath during said time interval, repeatedly adding to said bath during said time interval and as determined by respective ones of said pH measurements measured amounts of hydroxyl anions that are sufficient repeatedly substantially to restore said given initial pH thereof, repeatedly adding to said bath during said time interval measured amounts of nickel cations that are respectively related substantially in a first fixed proportion` to the measured amounts of hydroxyl anions added thereto, and repeatedly adding to said bath during said time interval measured amounts of hypophosphite anions that are respectively related substantially in a second fixed proportion to the measured amounts of nickel cations added thereto, said repeated measured additions of nickel cations and of hypophosphite anions repeatedly substantially restoring said given initial composition of said bath.

ll. The continuous process of chemically plating with nickel a solid body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper,ysilver, gold, palladium and platinum, which consists of providing an aqueous chemical nickel plating bath of the nickel cation-hypophosphite anion type and having both a given'4 initial composition and a given initial pH, contacting said body with said bath during a time interval in order to effect the reduction of nickel cations to metallic nickel and the deposition thereof upon the surface of said body along with the companion oxidation of hypophosphite anions to phosphite anions and resulting in the tendency of depletion of both nickel cations and hypophosphite anions in said bath and in the corresponding tendency of decrease in the pH thereof, measuring the pH of said bath during said time interval, continuously adding to said bath during said time interval and as determined by said pH measurement hydroxyl anions at a measured rate that is sufficient substantially to maintain said given initial pH thereof, continuously adding to said bath during said time interval nickel cations at a measured rate that is related substantially in a first fixed proportion to the measured rate of addition of hydroxyl anions thereto, and continuously adding to said bath during said time interval hypophosphite anions at a measured rate that is related substantially in a second fixed proportion to the measured rate of addition of nickel cations thereto, said continuous measured rate additions of nickel cations and of hypophosphite anions substantially maintaining said given initial composition of said bath.

l2. The continuous process of chemically plating with nickel a solid body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which consists of providing an aqueous chemical nickel plating bath of the nickel cation-hypophosphite anion type and having both a given initial composition and a given initial pH, preparing a first aqueous stock solution containing a fixed amount of hydroxyl anions per liter,

preparing a second aqueous stock solution containing a xed amount of nickel cations per liter, preparing a third aqueous stock solution containing a fixed amount of hypophosphite anions per liter, contacting said body with said `bath during a time interval in order to effect the reduction of nickel cations to metallic nickel and the deposition thereof upon the surface of said body along with the companion oxidation of hypophosphite anions to phosphite anions and resulting in the depletion of both nickel cations and hypophosphite anions in said bath and in the corresponding decrease in the pH thereof, measuring the pH of said bath during said time interval, adding to said bath during said time interval and as determined by said pH measurement a measured amount of said first stock solution that is sufiicient substantially to restore said given initial pH thereof, adding to said bath during said time interval a measured amount of said second stock solution that is related substantially in a first fixed proportion to the measured amount of said first stock solution added thereto, and adding to said bath during said time interval a measured amount of said third stock solution that is related substantially in a second fixed proportion to the measured amount of said second stock solution added thereto, said measured additions of said second stock solution and of said third stock solution substantially restoring said given initial composition of said bath.

13. The continuous process of chemically plating with nickel a solid body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which consists of providing an aqueous chemical nickel plating bath o-f the nickel cation-hypophosphite anion type and having both a given initial composition and a given initial pH, preparing a first aqueuos stock solution of hydroxyl anions of C molar concentration, preparing a second aqueousy stock solution of nickel cations of C molar concentration, preparing a third aqueous stock solution of hypophosphite anions of C molar concentration, contacting said body With said bath during a time interval in order to effect the reduction of nickel cations to metallic nickel and the deposition thereof upon the surface of said body along with the companion oxidation of hypophosphite anions to phosphite anions and resulting in the depletion of both nickel cations and hypophosphite anions in said bath and in the corresponding decrease in the pH thereof, measuring the pH of said bath during said time interval, adding to said bath during said time interval and as determined by said pH measurement a measured volume V of said first stock solution that is sufficient substantially to restore said given initial pH thereof, adding to said bath during said time interval a measured volume AV of said second stock solution, and adding to said bath during said time interval a measured volume BAV of said third stock solution, said measured volume additions of said second stock solution and of said third stock solution substantially restoring said given initial composition of said bath, Where V is a variable as requiredand Where C and A and B are fixed constants.

14. The continuous process of chemically plating with nickel a solid `body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which consists of providing an aqueous chemical nickel plating bath of the nickel cation-hypophosphite anion type and having both a given initial composition and a given initial pH, preparing a first aqueous 'stock solution of hydroxyl anions of C molar concentration, preparing a second aqueous stock solution of nickel cations of AC molar concentration, preparing a third aqueous stock solution of hypophosphite anions of BAC molar concentration, where C and A and B are fixed constants, contacting said body with said bath during a time interval in order to edect the reduction of nickel cations to metallic nickel and the deposition thereof upon the surface of said body alo-ng With the companion oxidation of hypophosphite anions to phosphite anions and resulting in the depletion of both nickel cations and hypophosphite anions in said bath and in the corresponding decrease in the pH thereof, measuring the pH of said bath during said time interval, adding to said bath during said time interval and as determined by said pH measurement a measured volume V of said first stock solution that is suticient substantially to restore said given initial pH thereof, where V is a variable as required, and also adding to said bath during said time interval substantially equal measured volumes V of said second 'stock solution and of said third stock solution, said measured volume additions of said second stock solution and of said third stock solution substantially restoring said given initial composition of said bath.

l5. The continuous process of chemically plating with nickel a solid body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which consists of providing an aqueous chemical nickel plating bath of the nickel cation-hypophosphite anion type and having both a given initial composition and a given initial pH, contacting said body with said bath during a time interval in order to eiect the reduction of nickel cations to metallic nickel and the deposition thereof upon the surface of said body along with the companion oxidation of hypophosphite anions to phosphite anions and resuiting in the depletion of both nickel cations and hypophosphite anions in said bath and in the corresponding decrease in the pH thereof, measuring the pH of said bath during said time interval, initiating the addition of hydroxyl anions to said bath only in response to a measurement indicating a predetermined reduction in the pH thereof from said given initial pH, arresting the addition of hydroxyl anions to said bath only in response to a measurement indicating a substantial restoration of the pH thereof to said given initial pH, establishing the measured amount of hydroxyl anions thus added to said bath, adding to said bath during said time interval a measured amount of nickel cations that is related substantially in a rst iixed proportion to the measured amount of hydroxyl anions added thereto, and adding to said bath during said time interval a measured amount of hypopho-sphite anions that is related substantially in a second fixed proportion to the measured amount of nickel cations added thereto, said measured additions of nickel cations and of hypophosphite anions substantially restoring said given initial composition of said bath.

16. rThe continuous process set forth in claim l5, wherein said additions of nickel cations and of hypophosphite anions to said bath are made thereto at least partially concurrently vvith said establishment of the measured amount of hydroxyl anions added thereto.

17. The continuous process of chemically plating with nickel a solid body essentially comprising an element selected from the group co-nsisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which consists of providing an aqueous chemical nickel plating bath of the nickel cation-hypophosphite anion type and having both a given initial composition and a given initial pH, contacting said body with said bath during a time interval in order to etfect the reduction of nickel cations to metallic nickel and the deposition thereof upon the surface of said body along with the cornpanion oxidation of hypophosphite anions to phosphite anions and resulting in the depletion of both nickel cations and hypophosphite anions in said `bath and in the corresponding decrease in t-e pH thereof, measuring the pH of said bath during said time interval, adding to said bath during said time interval and as determined by said pH measurement a measured amount of hydroxyl anions that is sufficient substantially to restore said given initial pH thereof, adding to said bath during said time interval a measured amount of nickel cations that is related substantially in a iixed proportion to the measured amount of hydroxyl anions added thereto, and adding to said bath during said time interval a measured amount of hypophosphite anions that is suficient substantially to restore the concentration thereof to that of said given initial composition of said bath, said measured additions of nickel cations and of hypophosphite anions substantially restoring said given initial composition of said bath.

References Cited in the file of this patent UNITED STATES PATENTS Brenner Dec. 5, 1950 Talmey et al Nov. l0, i953 OTHER REFERENCES UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 29872;?353 February 3, l959 Donald E Metheny It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column l29 line 55, before "pH" insert M given initial mi; line 55*y after "Corresponding" insert 4m given initial line 59, after "6.5" and before the period insert ma of said bath met,

Signed and sealed this 26th day of May 1959o KARL AXLINE ROBERT C. WATSON Attesting Ocer Commissioner of Patents 

1. THE CONTINUOUS PROCESS OF CHEMICALLY PLATING WITH NICKEL A SOLID BODY OF CATALYTIC MATERIAL, WHICH CONSISTS OF PROVIDING AN AQUEOUS CHEMICAL NICKEL PLATING BATH OF THE NICKEL CATION-HYPOPHOSPHITE ANION TYPE AND HAVING BOTH A GIVEN INITIAL COMPOSITION AND A GIVEN INITIAL PH, CONTACTING SAID BODY WITH SAID BATH DURING A TIME INTERVAL IN ORDER TO EFFECT THE REDUCTION OF NICKEL CATIONS TO METALLIC NICKEL AND THE DEPOSITION THEREOF UPON THE SURFACE OF SAID BODY ALONG WITH THE COMPANION OXIDATION OF HYPOPHOSPHITE ANIONS TO PHOSPHITE ANIONS AND RESULTING IN THE DEPLETION OF BOTH NICKEL CATIONS AND HYPOPHOSPHITE ANIONS IN SAID BATH AND IN THE CORRESPONDING DECREASE IN THE PH THEREOF, MEASURING THE PH OF SAID BATH DURING SAID TIME INTERVAL ADDING TO SAID BATH DURING SAID TIME INTERVAL AND AS DETERMINED BY SAID PH MEASUREMENT A MEASURED AMOUNT OF ALKALIZING REAGENT THAT IS SUFFICIENT SUBSTANTIALLY TO RESTORE SAID GIVEN INITIAL PH THEREOF, ADDING TO SAID BATH DURING SAID TIME INTERVAL A MEASURED AMOUNT OF NICKEL CATIONS THAT IS RELATED SUBSTANTIALLY IN A FIRST FIXED PROPORTION TO THE MEASURED AMOUNT OF ALKALIZING REAGENT ADDED THERETO, AND ADDING TO SAID BATH DURING SAID TIME INTERVAL A MEASURED AMOUNT OF HYPOPHOSPHITE ANIONS THAT IS RELATED SUBSTANTIALLY IN A SECOND FIXED PROPORTION TO THE MEASURED AMOUNT OF NICKEL CATIONS ADDED THERETO, SAID MEASURED ADDITIONS OF NICKEL CATIONS AND OF HYPOPHOSPHITE ANIONS SUBSTANTIALLY RESTORING SAID GIVEN INITIAL COMPOSITION OF SAID BATH. 